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Biomedical subjects

N Akamatsu

Publications and source records attributed to N Akamatsu.

At least 109 records · Page 6Linked to original sources
PubMed1985

Decreased transfer of oligosaccharide from oligosaccharide-lipid to protein acceptors in regenerating rat liver.

The transfer of [14C]glucose from UDP-[14C]glucose to lipid intermediates and glycoproteins was decreased in regenerating rat liver microsomes 24 h after partial hepatectomy. In regenerating liver microsomes, the concentration of free dolichyl phosphate (Dol-P) was significantly decreased. However, it was only about 10% of total Dol-P, which was not significantly changed. On the addition of exogenous Dol-P, the transfer of [14C]glucose to glycoproteins was still decreased, while the decrease of the transfer to lipid intermediates was no longer observed. These results suggest that the glycoprotein synthesis is not regulated by the amount of Dol-P in regenerating liver microsomes. Oligosaccharide obtained from [14C]glucosyl-oligosaccharide-lipid was not distinguishable between regenerating liver and control by paper chromatography. The oligosaccharide transfer to protein in microsomes was compared by using [14C]glucosyl-oligosaccharide-lipid as oligosaccharide donor. The transfer of oligosaccharide to endogenous proteins decreased to 77% of control in regenerating liver and the transfer to exogenously added denatured alpha-lactalbumin decreased to 59% of control. Therefore, it is unlikely that the acceptor capacity of endogenous protein is decreased in regenerating liver. Neither the change in oligosaccharide-lipid under the condition for oligosaccharide transfer assay nor the stability of oligosaccharide transferase was different between regenerating liver and control. These results strongly suggest that the decrease in the activity of the oligosaccharide transferase in microsomes causes the decrease of glycoprotein synthesis in regenerating liver, which was shown in our previous studies.

Animals↗
PubMed1985

Age-related alterations in the catecholamine-sensitive adenylate cyclase system of the prostate.

Considerably reduced responses to stimulation by isoproterenol of adenylate cyclase activity of prostatic membranes were observed in 12- to 18-month-old rats, compared to 3-month-old animals. Plasma testosterone levels were significantly lower in 18-month-old rats, while 12-month-old animals showed levels similar to those present in young ones. A decrease in isoproterenol activation of adenylate cyclase was not associated with a fall in beta-adrenergic receptor sites. Guanine triphosphate and 5'-guanylylimidodiphosphate (Gpp(NH)p) were effective in potentiation of isoproterenol activation of adenylate cyclase and altering the affinity of beta-adrenergic receptors for the agonist in membranes from young rats but not from the aged. The age-induced refractoriness to isoproterenol or Gpp(NH)p was observed without a significant loss in NaF-stimulated activity. Prior incubation of aged membranes with isoproterenol and GMP restored subsequent stimulation by Gpp(NH)p, presumably due to the clearance of inhibitory GDP tightly bound to the guanine nucleotide regulatory components in aged membranes. These results indicate that the dysfunction in the adenylate cyclase system of old prostates may not be related to a modification in the beta-adrenergic receptor per se, but to, in part, a defect in the interaction of activating guanine nucleotides with regulatory components of the adenylate cyclase system.

Adenylyl Cyclases↗
PubMed1985

Stimulation of protein glycosylation in cultured hepatoma cells by polyprenyl phosphates.

The aim of this work was to selectively stimulate N-glycosylation of proteins in cultured AH 70Btc hepatoma cells. Dolichyl phosphate, alpha-dihydrodecaprenyl phosphate and solanesyl phosphate were entrapped in egg lecithin liposomes and supplied to the cells. After treatment with 0.6-15 nmol of the polyprenyl phosphates/3 ml/dish for 48 hr, the incorporations of [14C]glucosamine into N-linked saccharide chains of glycoproteins and into lipid intermediates were increased to various extents. The stimulation by alpha-dihydrodecaprenyl phosphate was most significant and 15 nmol of the lipid/dish increased the incorporation into N-linked saccharide chains of glycoproteins by about 80%. The incorporations of [14C]glucosamine into O-linked saccharide chains and of [14C]leucine into proteins were not changed significantly by alpha-dihydrodecaprenyl phosphate. When the N-linked glycopeptides prepared from the cells and those from the cells treated with the polyprenyl phosphate were compared by Sephadex G-50 column chromatography, no significant difference was observed. Analysis of reduced cellular glycoproteins by sodium dodecyl sulfate/polyacrylamide-gel electrophoresis showed that alpha-dihydrodecaprenyl phosphate increased the incorporation of [14C]glucosamine into N-linked saccharide chains of certain high-molecular-weight glycoproteins. In addition, the polyprenyl phosphate enhanced the adhesiveness of the cells to the substratum, probably as a result of the stimulation of N-glycosylation of proteins.

Animals↗
PubMed1984

Alterations in N-linked oligosaccharides of glycoproteins during rat liver regeneration.

[3H]Mannose-labeled glycopeptides in the slices after partial hepatectomy were characterized by column chromatography using Sephadex G-50, DE-52 and Con A-Sepharose, and further by digestion with alpha-mannosidase and endo-beta-N-acetylglucosaminidase H. They contained both 'complex type' and 'high-mannose type' oligosaccharides. A higher proportion of 'complex type' oligosaccharides was contained in regenerating liver 24 h after partial hepatectomy than in control. This tendency was increased gradually with time and was most pronounced at 144 h. In our previous studies, the activities of microsomal N-acetylglucosaminyltransferase towards endogenous and exogenous acceptors at 144 h after partial hepatectomy were shown to exceed most prominently that in control. No differences in the oligosaccharides were observed at 240 h when the deficit of liver had been restored. The oligosaccharides of glycopeptides in the incubation media were mostly 'complex type' and the differences between regenerating liver and control were observed only at 144 h. These results suggest that oligosaccharide processing of glycoproteins is regulated at the transfer step of peripheral N-acetylglucosamine to core oligosaccharides 144 h after partial hepatectomy, and that these alterations in oligosaccharides of glycoproteins may be related to hypertrophy and hyperplasia of hepatic cells in liver regeneration.

Animals↗
PubMed1984

Stimulation of prostaglandin E2 synthesis by exogenous phospholipase A2 and C in rabbit kidney medulla slices.

We have investigated the effects of phospholipase A2 and C on the synthesis of prostaglandin E2 in rabbit kidney medulla and the release of fatty acids from the medulla slices. Exogenous phospholipase A2 [from Naja naja (Indian cobra) venom] and phospholipase C (from Clostridium welchii) stimulated prostaglandin E2 production in a dose-dependent manner. At the maximal effective concentrations (0.5 unit of phospholipase A2/ml, 2 units of phospholipase C/ml), phospholipase C increased prostaglandin E2 formation to the level observed with phospholipase A2. Phospholipase A2 enhanced the release only of unsaturated fatty acids, whereas phospholipase C stimulated the release of individual free fatty acids (C 16:0, C 18:0, C 18:1, C 18:2 and C 20:4). Moreover, p-bromophenacyl bromide inhibited phospholipase A2-stimulated prostaglandin E2 production and the release of fatty acids, but it had no influence on prostaglandin E2 formation and the release of fatty acids increased by phospholipase C, indicating that the stimulatory effect of phospholipase C is not mediated through the activation of endogenous phospholipase A2. These results suggest the presence of diacylglycerol lipase and monoacylglycerol lipase in the kidney and the importance of this pathway in prostaglandin synthesis by the kidney.

Acetophenones↗
PubMed1983

Effects of dibutyryl cyclic AMP on the syntheses of dolichol-linked saccharides and glycoproteins in cultured hepatoma cells. Correlation with the effect on the adhesiveness of the cells.

When the hepatoma cells (AH 70Btc, Clone 10-5) were cultured in the presence of 1 mM-dibutyryl cyclic AMP for 2 days, the incorporation of [14C]glucosamine into protein was increased over 2-fold. At the same time, dibutyryl cyclic AMP increased the incorporation of [14C]glucosamine into dolichol-linked N-acetylglucosamine and NN'-diacetylchitobiose about 1.5-fold and into dolichol-linked oligosaccharides about 3-fold. Analysis of cellular glycoproteins by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis after reduction showed that dibutyryl cyclic AMP specifically enhanced the glycosylation of a fibronectin-like glycoprotein with an apparent mol.wt. of 220 000 and two other high-molecular-weight glycoproteins (apparent mol.wts. 270 000 and 185 000). Increased glycosylation of the glycoproteins with mol.wts. of 220 000 and 185 000 was shown to be linked to increased synthesis of the polypeptide portion. In addition to the above effects, dibutyryl cyclic AMP enhanced the adhesiveness of AH 70Btc cells to glass surfaces. Both the effects on the glycosylation pathway and on adhesiveness of cells were reversed by further treatment of the cells with 1 microgram of tunicamycin/ml. The results indicated that dibutyryl cyclic AMP increased the synthesis of dolichol-linked oligosaccharides and N-glycosylation of proteins in AH 70Btc cells. The enhancement of adhesiveness may be mediated by the increased synthesis of dolichol-linked oligosaccharides and also may be related to the increased synthesis of fibronectin.

Animals↗
PubMed1983

A clinical study of the results of cementless total hip replacement.

We introduce our total hip prosthesis, its operation technique, and report the clinical results. Ours does not use bone-cement, but its design, together with the use of original bone and new bone formation surrounding it, results in a biological anchoring. Since 1978, we developed for this new type of total hip prosthesis 6 sizes of stem to fit more rigidly within the intramedullary canal of femur. The new femoral component also has larger notches on its surface than did the old one. Our results of 144 cases (147 joints) ranging from 2 to 10 postoperative years giving an average of 4.4 years, are quite satisfactory. Blood loss during the operation is as little as 480 ml. The few complications observed differ from those of the Charnley type, and will be reduced greatly when the operation is yet more cautiously and skillfully done. Unilateral replacement in bilaterally affected patients improved the condition of the unoperated side in 30% of the cases.

Adult↗
PubMed1983

Mechanism of increased susceptibility to 4-nitroquinoline-1-oxide in cultured skin fibroblasts from patients with familial polyposis coli.

About 50% of the strains of cultured fibroblasts from patients with familial polyposis coli (FPC) exhibited increased susceptibility to cytotoxicity of 4-nitroquinoline-1-oxide (4NQO) compared with cells from normal individuals. The FPC cells that showed hyper-sensitivity to 4NQO were also hyper-sensitive to mitomycin C (MMC), but susceptibilities of these cells to UV radiation, methyl methanesulfonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were within the normal range. The extent of single-strand scission of DNA in the 4NQO-sensitive FPC cells was greater than in normal cells, and the amount of [14C]4NQO bound to DNA in the FPC cells was twice as high as in normal cells. The rate of release of [14C]4NQO from DNA by the post-culture was the same as in both FPC and normal cells. The 4NQO-sensitive FPC cells exhibited increased 4NQO-reductase activity; the level of this activity was consistent with the extent of the decrease in colony formation by 4NQO. These results suggest that the enhanced ability to activate 4NQO might be an important factor in the mechanism of susceptibility of FPC cells to 4NQO rather than the reduced ability to repair DNA.

4-Nitroquinoline-1-oxide↗
PubMed1983

Susceptibility of skin fibroblasts from patients with retinoblastoma to transformation by murine sarcoma virus.

Cultured skin fibroblasts from patients with retinoblastoma (RB) of different etiology have been studied for their susceptibility to transformation by murine sarcoma virus. The cells from patients with a deletion in chromosome 13 (13q-) and those from sporadic unilateral cases due to somatic mutation were as sensitive as normal cells. However, the cells from familial cases showed an extremely high sensitivity to transformation. Moreover, in familial cases the susceptibility was significantly higher in bilaterally affected patients than in unilateral cases. These findings suggest that the heritable RB gene is different from 13q- and its degree of expression is also manifest at the cellular level.

Cell Transformation, Viral↗
PubMed1982

The direct fixation system of total hip prosthesis. Research of the possibilities of fixing total hip prosthesis directly to bone.

There are two methods for the fixation of prostheses to bone; one is a method using bone cement and another is the direct fixation of the prostheses to bone. Four types of animal experiments were performed to compare the two methods of fixation. A small pyramid shaped test piece was used to compare the fixation capacity of the socket spike. Also, a special test piece was used to study the time of bone formation, to check the fixation capacity of bone bar formation occurring in the hole in the based part of the prosthetic component. furthermore, models of prosthetic stem and socket were made and attached to the femur and ilium of dog to perform fixation tests and fatigue tests. As a result, any of the tests proved that the direct fixation method without the usage of bone cement was superior to the fixation method using bone cement.

Acetabulum↗
PubMed1982

A cementless system of total hip prosthesis. Experimental studies on total hip prosthesis in dogs.

It is essential that the prosthetic material should not be harmful to the human body, it should be strictly fitted to the body and it should have sufficient durability. To investigate those conditions of an artificial joints as mentioned above, it is important to have experimental studies using a model of the artificial joint in animals instead of a simulator. The authors have developed their own total hip prosthesis for a dog since 1970. These prostheses were fixed to the bone without bone cement. These dogs were killed periodically from 8 weeks to 3 years after surgery of total hip replacement. Not only were pathohistological studies on the joint capsule and bony tissue of the femur surrounding the prosthesis performed, but also scanning electron microscopic examination on capsule and the surface of the prosthetic head were performed. The results were excellent. Ther was no loosening or wear when the new type of acetabular socket with large spikes was used. On the other hand, in the case of the old type socket with its smooth surface and smaller spikes, loosening of the socket and prosthetic stem occurred within one year after surgery.

Animals↗